topic 2

Question 1

major episode in the history of life (2)

Answer 1

• earth formed 4.6 billion years ago

- 3.8 billion years old C-isotopes in greenland

Question 2

conditions of earth (4.6 bill. yrs ago - 4)

Answer 2

• more frequent and intense lightening
• volcanic activity
• primitive atmosphere with CH4, NH3, CO2, N2, H2, and H2O
• no O3 layer

Question 3

no O3 layer means

Answer 3

intense UV radiation “reducing” atmosphere

Question 4

first living organism (2)

Answer 4

• probably prokaryotic

- stromatolites

Question 5

prokaryotic

Answer 5

cell lacking membrane bound organelles

Question 6

stromatolites (2)

Answer 6

• 3.5 billion years old

- dome-shaped sedimentary rocks